This section provides background information related to the present disclosure which is not necessarily prior art. This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
According to the present teachings, a piezoelectric vibration energy harvester, having a piezoelectric beam, is provided to generate electricity under the weight of passing cars or crowds. The piezoelectric beam buckles to a controlled extent when the device is stepped on or otherwise depressed. The energy harvester can have horizontal or vertical configuration. Horizontal configuration is easier to install and can be tuned to low passing loads. The moving element of the device is one or more piezoelectric beams, such as a uniform bimorph beam or a segmented beam. The ends of the segmented beam are simple spring steel or brass while the central span is a piezoelectric bimorph.
The piezoelectric beam is horizontal in the horizontal configuration. In this configuration, the vertical vehicle load is transferred to a horizontal buckling force through a scissors-like mechanism. The mechanism consists of seven rigid links. In the vertical configuration, the piezoelectric beam is vertical and directly sustains the vehicle load. The vertical (direct) configuration is designed to buckle under the load of the vehicle. This results in significant deformation of the piezoelectric and generates substantial amounts of power. If the beam's buckling is not controlled, it will result in the fracture of the beam. The buckling deformation of the beam is constrained by limiting its axial deformation.
To better control the axial deformation of the buckled beam, the deformation has to be noticeable. This requires the length of the beam to be long. As the length of the beam increases its axial deformation becomes more significant. To reduce the cost of the present energy harvester, a segmented beam is preferred over a uniform beam for the buckling component. This choice allows having large axial deformation without more usage of costly piezoelectric.
In the present disclosure, the energy harvester is analytically modeled. The electro-mechanical coupling and the geometric nonlinearities have been included in the model for the piezoelectric beam. The design criteria for the device are discussed. It is demonstrated that the device can be realized with commonly used piezoelectric patches and can generate hundreds of milliwatts of power. The effect of the design parameters on the generated power and required tolerances are illustrated.
The present device could be implemented in the sidewalks producing energy from the weight of people passing over it. Other possible applications are portable smart phones chargers and shoe heel energy harvesting. The dance floor of a club is another applicable example for using this harvester. The vertical device could be implemented in roads, using the weight of the passing cars for generating electricity. The device is not prone to resonance and generates notable amounts of power from passing of each tire. It therefore can be used as a self-sufficient sensor for traffic control.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.